• Carlos Garnacho's avatar
    ACPI / battery: Add sysfs representation after checking _BST · 12c78ca2
    Carlos Garnacho authored
    Thus move sysfs_add_battery() after acpi_battery_get_state(), which doesn't
    require the power_supply. Prevents possible hanged tasks if
    acpi_battery_get_state() fails consistently (and takes a long time in doing
    so) when called inside acpi_battery_add().
    
    In this situation the battery module first calls sysfs_add_battery(),
    which creates a power_supply, which spawns an async
    power_supply_deferred_register_work() task, which shall try to hold the
    parent battery device mutex (being already held) so this register work
    is set up after device initialization. If initialization takes long enough
    the thread will be eventually run and try to hold the mutex before
    acpi_battery_add() had the chance to finish.
    
    Eventually the 5 retries in acpi_battery_update_retry() fail, the error
    state is propagated, and results in sysfs_remove_battery() being called
    within the error handling paths of acpi_battery_add(), and the power_supply
    tear down too.
    
    This triggers a cancel_delayed_work_sync() of the deferred_register_work
    task, which ends up in schedule(). The end result is that the deferred
    task is blocked trying to acquire the parent device mutex, which is not
    released because the thread doing initialization (and failure handling)
    went to sleep awaiting for the deferred task to be cancelled.
    
    The hanged tasks look like this:
    
    INFO: task kworker/u8:0:6 blocked for more than 120 seconds.
     ...
    Call Trace:
     [<ffffffff815daec5>] schedule+0x35/0x80
     [<ffffffff815dda3c>] schedule_timeout+0x1ec/0x250
     [<ffffffff810a0572>] ? check_preempt_curr+0x52/0x90
     [<ffffffff810a05c9>] ? ttwu_do_wakeup+0x19/0xe0
     [<ffffffff815db915>] wait_for_common+0xc5/0x190
     [<ffffffff810a1500>] ? wake_up_q+0x70/0x70
     [<ffffffff815db9fd>] wait_for_completion+0x1d/0x20
     [<ffffffff8108ffb1>] flush_work+0x111/0x1c0
     [<ffffffff8108dfe0>] ? flush_workqueue_prep_pwqs+0x1a0/0x1a0
     [<ffffffff810909af>] __cancel_work_timer+0x9f/0x1d0
     [<ffffffff81090b13>] cancel_delayed_work_sync+0x13/0x20
     [<ffffffff8147ac67>] power_supply_unregister+0x37/0xc0
     [<ffffffffa058b03d>] sysfs_remove_battery+0x3d/0x52 [battery]
     [<ffffffffa058bf3a>] acpi_battery_add+0x112/0x181 [battery]
     [<ffffffff81366db6>] acpi_device_probe+0x54/0x19b
     [<ffffffff81427e9c>] driver_probe_device+0x22c/0x440
     [<ffffffff81428181>] __driver_attach+0xd1/0xf0
     [<ffffffff814280b0>] ? driver_probe_device+0x440/0x440
     [<ffffffff8142591c>] bus_for_each_dev+0x6c/0xc0
     [<ffffffff8142758e>] driver_attach+0x1e/0x20
     [<ffffffff81426fc3>] bus_add_driver+0x1c3/0x280
     [<ffffffff81428b00>] driver_register+0x60/0xe0
     [<ffffffff81366c80>] acpi_bus_register_driver+0x3b/0x43
     [<ffffffffa0591040>] acpi_battery_init_async+0x1c/0x1e [battery]
     [<ffffffff81099268>] async_run_entry_fn+0x48/0x150
     [<ffffffff81090d09>] process_one_work+0x1e9/0x440
     [<ffffffff81090fab>] worker_thread+0x4b/0x4f0
     [<ffffffff81090f60>] ? process_one_work+0x440/0x440
     [<ffffffff81096b58>] kthread+0xd8/0xf0
     [<ffffffff815de97f>] ret_from_fork+0x1f/0x40
     [<ffffffff81096a80>] ? kthread_worker_fn+0x180/0x180
    
    INFO: task kworker/u8:4:282 blocked for more than 120 seconds.
     ...
    Call Trace:
     [<ffffffff810ad745>] ? put_prev_entity+0x35/0x8b0
     [<ffffffff815daec5>] schedule+0x35/0x80
     [<ffffffff815db14e>] schedule_preempt_disabled+0xe/0x10
     [<ffffffff815dc533>] __mutex_lock_slowpath+0xb3/0x120
     [<ffffffff815dc5bf>] mutex_lock+0x1f/0x30
     [<ffffffff8147a59b>] power_supply_deferred_register_work+0x2b/0x50
     [<ffffffff81090d09>] process_one_work+0x1e9/0x440
     [<ffffffff81090fab>] worker_thread+0x4b/0x4f0
     [<ffffffff81090f60>] ? process_one_work+0x440/0x440
     [<ffffffff81090f60>] ? process_one_work+0x440/0x440
     [<ffffffff81096b58>] kthread+0xd8/0xf0
     [<ffffffff815de97f>] ret_from_fork+0x1f/0x40
     [<ffffffff81096a80>] ? kthread_worker_fn+0x180/0x180
    
    Making sysfs_add_battery() the last operation here means that the
    power_supply won't be created yet when the acpi_add_battery() failure
    handling happens, the deferred task won't even spawn, and
    sysfs_remove_battery will just skip over the NULL battery->bat.
    Signed-off-by: default avatarCarlos Garnacho <carlosg@gnome.org>
    Signed-off-by: default avatarRafael J. Wysocki <rafael.j.wysocki@intel.com>
    12c78ca2
battery.c 38 KB